Antiochus III (241-187 B.C.) was a Syrian king of the Seleucid dynasty, Alexander the Great's successors in Asia. Antiochus attempted to restore Alexander's empire to its former greatness, and the magnitude of this undertaking earned Antiochus the name Megas, "the Great."
The second son of Seleucus II and his wife Laodice, Antiochus was born in Babylonia. When his older brother, Seleucus III, was assassinated in Phrygia in 223, Antiochus succeeded him as king at the age of 18. His cousin Achaeus assumed military command and punished Seleucus's assassins. There was strong public support for Achaeus to ascend the throne, but he declined and remained loyal to his cousin. Achaeus governed in Asia Minor.
In 222 Molon and Alexander, the satraps of Media and Persia, revolted. Molon proclaimed himself independent and king, but by 220 his forces had abandoned him, and he and Alexander committed suicide. Then Achaeus sought power and occupied Antioch, but the populace deserted him. Antiochus foolishly overlooked the brief insurrection and instead prepared to attack Egypt. His forces easily gained coastal Phoenicia, Tyre, and Ptolemais, but Antiochus faltered at the fortress of Dora in northern Palestine. This gave Egypt a chance to reorganize its army, and on June 22, 217, Antiochus was defeated in Gaza by Ptolemy IV Philopater. Achaeus grew more and more independent, and the Parthian Arsacids in the northeast gained power. But in Jerusalem the Jews welcomed Antiochus and hailed his confirmation of their religious privileges.
In the winter of 217/216, Antiochus prepared to face the now-powerful Achaeus, and after 2 years of war Antiochus cornered him in Sardis. Through Cretan intrigue Achaeus was captured, mutilated, and then beheaded. Antiochus thus regained his western capital, but the powerful city of Pergamon still remained hostile.
Antiochus then set out to restore the former boundaries of the Seleucid empire. Between 212 and 204 he campaigned in Armenia, regained Parthia and Bactria as vassal kingdoms, and led expeditions into the Kabul Valley in India and across the Persian Gulf into Arabia. About 210 Antiochus made his 10-year-old son Antiochus coruler, as he feared his own death in these campaigns. In 204 Antiochus regained Phoenicia and southern Palestine from Egypt, for in that year Ptolemy IV had died and left his throne to his 4-year-old son Ptolemy V Epiphanes. Antiochus and Philip V of Macedon then decided to divide the Ptolemaic empire.
Fearing the growing strength of Antiochus, Rome dispatched its envoy in 200 to protect Egypt and halt Antiochus, but he disregarded the weak ultimatum. In 197 Antiochus again campaigned in Asia Minor to gain Ptolemaic territories. With Philip's defeat in Greece showing his weakness and with the Ptolemaic empire in distress, Antiochus began to dream of reuniting Alexander's empire. Rome, however, now proclaimed itself champion of Greece's liberty, and Rhodes sought to block Antiochus. After campaigning in Europe, rumors of intrigue regarding Egypt brought Antiochus back to Antioch in 196, where he met and welcomed the defeated Hannibal.
When Antiochus's son died suddenly in 193, rumors of assassination flourished, the anti-Roman faction gained strength, and in 192 war erupted in Greece. Antiochus landed in Greece and surprised the Roman occupation forces. Macedon deserted him and joined Rome, and many of the Greek states vacillated in their loyalties. Roman countercampaigns in 191 forced Antiochus to seek refuge in Chalkis and later in southern Thessaly, where he was defeated. After sea battles in the Aegean, Antiochus feared a Roman invasion of Asia Minor, which finally occurred in 190. Antiochus again met defeat at Magnesia, and the Peace of Apemea in 188 ended a century of Seleucid dominance in Asia Minor. Leaving his son Seleucus in Syria as coruler, Antiochus departed for Luristan, and in the following year he was killed by hostile tribesmen.
Edwyn Robert Bevan, The House of Seleucus (2 vols., 1902; repr. 1966), still provides the most thorough discussion of Antiochus III and the Seleucid empire. Pierre Grimal and others, Hellenism and the Rise of Rome (1965; trans. 1968), is disappointing in its discussion of Antiochus, as is W. W. Tarn, Hellenistic Civilization (1927; 3d rev. ed., with G. T. Griffith, 1952). For background material see W. W. Tarn, The Greeks in Bactria and India (1938; 2d ed. 1951), and M. Rostovtzeff, The Social and Economic History of the Hellenistic World (3 vols., 1941).